Gravity Probe B

Testing Einstein's Universe

Special & General Relativity Questions and Answers

What does the equation look like that shows how gravitational radiation
is
lost from the binary pulsar system?

What astronomers observed
in the Hulse-Taylor Pulsar was a was a decrease in
the orbital period
of the two neutron stars. From general relativity, it was
possible
to predict, mathematically, how the period ought to change in time
as
the binary system emitted gravitational energy during the time the
orbits
of the neutron stars were being 'circularized'. The predicted
formula
for the period change, P-dot, can be found in the excellent
book by
Stuart Shapiro and Saul Teukolsky Black holes, white dwarfs
and neutron
stars, and it looks like this:

P-dot = -1.202 x 10^-12 M2 (2.8278 - M2)

where M2 = 1.41 solar masses...the mass of one of the neutron stars determined
by observation and the application of Kepler's Laws. The result is the
predicted period change is p-dot = -2.40 x 10^-12 and the observed
value is -2.30 +/- 0.22 x 10^-12. This implies a better than 10 percent
disagreement between theory and observation, and thereby proves that
gravitational radiation leakage is the simplest explanation.